In gas turbine engines it is necessary to protect exhaust ducts from damaging hot core gases by providing an insulating liner. The liner is suspended within the exhaust duct such that a gap is maintained between an inner surface of the exhaust duct and an outer surface of the liner. To alleviate some of the heat imparted to the liner by the hot gases, cooling air is passed through the gap between the exhaust duct and liner. Thus, the exhaust duct and liner are subjected to different pressure and temperature gradients, which results in differing expansion and contraction rates and amounts for each structure.
Additionally, certain aircraft requirements can exacerbate these differing expansion and contraction rates. For example, for certain aircraft types it can be desirable to have thrust vectoring capability or low radar signature profiles. As such, the exhaust duct and liner must be tailored to meet these requirements. This requires repositioning of the exhaust duct for thrust vectoring capability. Further, low radar signature profiles often require complex shapes that vary along the length of the duct and liner.
In order to maintain the desired temperature and pressure profile along the exhaust duct and liner, it is important to maintain proper spacing between the exhaust duct and liner. It is known to use a plurality of liner brackets or liner hangers to suspend the liner within the exhaust duct. However, attaching liners to non-circular, i.e. complex shape, ducts is difficult due to the varying tolerances between the exhaust duct and liner. Traditional attachment methods require a measurement and selection of an appropriate shim at each liner attachment location. This is costly and time consuming as there may be hundreds of liner attachment locations for each gas turbine engine.